The present invention relates to a coating composition and more particularly to a solution of a hydrolyzed or partially hydrolyzed alkoxysilane, and a cross-linking polymeric resin (e.g., arylcyclobutene and polyphenylene resin) that produces a low dielectric constant polymer.
Hydrolyzed alkoxysilanes have been used as adhesion promoters or coupling agents for arylcyclobutene resins. However, these alkoxysilanes generally have not successfully coated substrates having surfaces composed of more than one material (e.g., a microelectronic device).
The hydrolyzed alkoxysilanes are typically used as a primer layer, i.e., they are applied to the substrate first, followed by application of the polymeric material. The alkoxysilanes are typically hydrolyzed to form aqueous and/or protic solutions before being applied as thin films. However, many organoalkoxy-silanes are not soluble in water and must be dissolved first in a compatible organic solvent, such as an alcohol. Unfortunately, upon application of the aqueous alkoxysilane/alcohol mixture, a discontinuous film may form which contains voids where the film has not covered the substrate.
It is also known that a hydrolyzed alkoxy-silane can be used as an adhesion promoter primer layer for arylcyclobutene resins. For example, in Proc. MRS, Vol. 323, pg. 365, 1994, Adhesion of Cyclotene.TM.(BCB) Coatings on Silicon Substrates, a prehydrolyzed solution of 3-methacryloxypropyltrimethoxysilane (MOPS) in methanol was used as an adhesion promoter for CYCLOTENE.TM.. However, the MOPS solution is extremely difficult to deposit uniformly, forming agglomerates on the surface, which leads to reliability problems when used in fabricated parts.
This is particularly evident when the substrate surface is comprised of more than one material such as a microelectronic device (e.g., integrated circuit, multichip module and flat panel display). A microelectronic device may be comprised of many materials that need to be adhered to by a coating. Materials at the surface of these devices may include, for example, silicon, aluminum, copper, tungsten, silver, gold, platinum, other polymers (e.g., epoxies, polyimides and polyamides), ceramics (e.g., silicas, titanium nitrides, silicon nitrides and silicon oxynitrides).
Currently, polyimide resins are generally the accepted polymeric material employed as thin film dielectrics in the electronics industry. However, polyimide resins tend to absorb water and hydrolyze which can lead to circuit corrosion. Metal ions may migrate into the dielectric polyimide layer requiring a barrier layer between the metal lines and polyimide dielectric. Polyimides may exhibit poor planarization and gap fill properties. Non-fluorinated polyimides may exhibit undesirably high dielectric constants.
Accordingly, it remains highly desirable to provide coating compositions that avoid one or more problems of the prior art such as one of those described above.